>>I was pondering putting in a few live cacti. I was thinking
>>that if I left the cacti potted and just covered it with
>>substrate it shouldn't be a problem.
You don' tknow what vfertilizers and insecticides might leech into the environment or be excavated and consumed.
>>Only thing I could think of that may be harmful is the spines
>>(or whatever they are called).
If there is ever a supposition of possible harm, why would you do it?
>>But since uros are a desert animal this shouldn't be a >>problem, should it?
What the other posters said, plus one point unmade:
Cactus are endemic to North and South America. All other "cactus" you may acquire are not cactus, but some other variation of succulent with varying levels of toicity, many of which tends towards high levels of toxicity.
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uromastyx geyri (Saharan/Nigerian), hardwickii (Indian),
macfadyeni (Somalian), ocellata (Sudanese), ornata (Ornate), benti pseudophilbyi